Photonic Crystals

Abstract

In this paper, we review the early motivation for photonic crystal research which was derived from the need for a photonic bandgap in quantum optics. This led to a series of experimental and theoretical searches for the elusive photonic bandgap structures: those three-dimensionally periodic dielectric structures which are to photon waves, as semiconductor crystals are to electron waves. We shall describe how the photonic semiconductor can be ‘doped’, producing tiny electromagnetic cavities. Finally, we shall summarize some of the anticipated implications of photonic band structure for quantum electronics and the prospects for the creation of photonic crystals in the optical domain.     

Polymer‐Based Photonic Crystals

In this report, we highlight the development of polymers as 1D photonic crystals and subsequently place special emphasis on the activities in self‐assembled block copolymers as a promising platform material for new photonic crystals. We review recent progress, including the use of plasticizer and homopolymer blends of diblock copolymers to increase periodicity and the role of self‐assembly in producing 2D and 3D photonic crystals. The employment of inorganic nanoparticles to increase the dielectric contrast and the application of a biasing field during self‐assembly to control the long‐range domain order and orientation are examined, as well as in‐situ tunable materials via a mechanochromic materials system. Finally, the inherent optical anisotropy of extruded polymer films and side‐chain liquid‐crystalline polymers is shown to provide greater degrees of freedom for further novel optical designs.     

Silicon‐Based Photonic Crystals

Photonic crystals can be thought of as optical analogues of semiconductors. Here recent advances in photonic crystals based on silicon are reviewed. After summarizing the theory of photonic bandgap materials, the preparation and linear optical properties of 1D, 2D, and 3D silicon‐based photonic crystals are discussed. Laterally structured porous silicon with a defect line is shown in the Figure.     

Photonic Bandgaps in Disordered Inverse‐Opal Photonic Crystals

Three‐dimensional photonic crystals with full bandgaps at optical wavelengths can be fabricated with inverse‐opal techniques. We have shown that the bandgap is extremely sensitive to the presence of geometric disorder in the crystals (see Figure). The bandgap closes completely with a disorder strength as small as under two percent of the lattice constant. This fragility persists even at very high refractive index contrasts and is attributed to the creation of a bandgap at high frequency bands (8–9 bands) in inverse‐opal crystals. This should impose severe demand on the quality of lattice uniformity.     

pH响应性光子晶体

响应性光子晶体(Responsive photonic crystals,RPCs)具有无毒、无标记、低消耗和裸眼可视的优点,pH响应性光子晶体(pH-RPCs)为食品安全、生物医药、水体环境等领域提供了一种简便的检测方式。目前主要发展了胶体粒子组装体/反蛋白石、层状堆叠和全息三种结构类型的pH-RPCs。本文在介绍光子晶体(Photonic crystals,PCs)pH响应原理的基础上,从制备方法、结构特点和pH响应性能(如灵敏度、响应时间、可视化)等方面对上述pH-RPCs进行了详细的综述,分析总结了它们各自的优势和不足,并对其未来的发展进行了展望。     

Superconductor-Semiconductor Metamaterial Photonic Crystals

We constructed theoretically one-dimensional photonic crystal (1DPC) by using a semiconductor metamaterial in the near-infrared range(NIR) which is composed of Al-doped Z n O(A Z O) and Z n O. The construction of this photonic crystal (PC) is based on a high-temperature superconductor material with the semiconductor metamaterial as constituent layers for this PC. The electromagnetic interactions with this periodic structure are investigated using the transfer matrix method (TMM) in the NIR range. The investigation shows that the reflectance spectra are depending on some parameters of the periodic structure such as the thicknesses of the constituent layers, temperature, and the angle of incidence.     

Photonic Crystals from Emulsion Templates

Macroporous titania, which undergoes transition to the rutile phase by calcination without collapse of the pore structure, is obtained by polymerizing a titania sol suspended around “colloidal crystals” of oil droplets. The deformable template counteracts cracking of the titania phase. The Figure shows a scanning electron micrograph of a rutile sample with 200 nm pores obtained by the method described.     

Optical Activity of Photonic Crystals

Abstract

We consider optically active photonic crystals. We propose a model structure and discuss the factors which determine optical activity by reference to this model.